3 relay cooling fan wiring - - - > question

I've got the relays wires labeled and sorted, I just have one question. Can someone confirm fan #2 positive and negative wires according to 944-LT1's wiring diagram?



Here's a picture... it looks crazy, but it's really not bad.



Thanks!

What gauge wire are you using for the fan relays? The pigtails that came on my relays seems very thin. I have this diagram if it helps you. http://www.ls1tech.com/forums/attachments/conversions-hybrids/240453d1278029972-question-ls1-pcm-cooling-fan-control-cooling-fans.gif

LOL... I can't understand that... The wiring on the relays I have is 14awg.

The computer controls the ground path for the three cooling fan relays. The relays are used to control the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes cooling fan relay #1 and both fans operate at low speed, since the fans are connected in series through cooling fan relay #3. Cooling fan relay #2 is open (not energized) and is not used for low speed operation of the fans. When maximum cooling is required, the PCM energizes all three cooling fan relays. The left fan is still powered through cooling fan relay #1, but is now grounded through cooling fan relay #3. The right fan is now powered directly through cooling fan relay #2 and both fans operated at high speed.

Thanks,

What wire is the positive wire on fan #2? Is the positive wire, terminal 87 on relay 1?

Nevermind... I just re-read what you wrote...

Are you using the factory fans?

If so, why are you going through all the trouble of rewiring them. All you have to do is hook up two simple wires from the PCM to the factory 2 speed relay and your done. NO wire size to worry about , NO wiring diagram to worry about , NO finding fuses and hiding everything to look right.

Admin wrote:Are you using the factory fans?

If so, why are you going through all the trouble of rewiring them. All you have to do is hook up two simple wires from the PCM to the factory 2 speed relay and your done. NO wire size to worry about , NO wiring diagram to worry about , NO finding fuses and hiding everything to look right.

I'm not using the factory fans. I had to buy a new fan setup because the shop that I sold my old engine to took my radiator and my old fans. I'm using fans from a v6 ford contour.

I never knew you could re-use the factory fan relays. I just seen the relay diagram posted and figured it was the way to correctly wire the fans. Remember, there's no instructions on anything on this car and I'm not a engineer or mechanic. Maybe someone should write a "complete" swap manual! Hint hint... lol

I'll be using the relays and harness I've created. I've already hid all the wires and I think it looks pretty good.

Now I am glad for dragging my feet on the wiring. So, the GM PCM will control the Porsche relays, without having to use the thermofan switch?

Yes.It's a two , simple ,wire hook up.

I've got the high speed and low speed fan wires ran to the front of the car. Can I just hook these two wires up to the old thermoswitch wires If I were to use the old fan relays?

Do the high speed and low speed wires need to be hooked straight to the relays themselves?

I've got my fans wired and I've confirmed that they're working properly; I ended up using the 3 relay setup. Thanks 944-LT1 for posting that diagram.
The car started first try after sitting all winter! I'm surprised since the gas in it is almost two years old. Next up is the brakes; I just got my hubs back from the machine shop and they're ready for the boxster rotors!

I am going to do the 3 relay setup after looking at the price of the Porsche fan relay.

Sticky this thread in electrical modifications or Wiki? Looks pretty useful for reference.

When hooking into the Porsche fan relay with the GM high and low speed fan relay wires, does the high speed fan relay wire hook to TF and low speed to TS in the diagram below?
https://servimg.com/view/14651638/20

I change my mind on the two wire hookup or 3 relay system on a daily basis. Today, I am all for simple.

IIRC the PCM HI/LOW FAN relay leads are called to ground (-)

The Porsche fan relay is ground activated from the thermofan switch for the fan motors, also. The high/lo fan relay wires from the GM ECM should splice into the Porsche coolant temperature switch wires going to the Porsche fan relay. GM Hi speed to the RT/WS (red/white) colored wire labeled TF on the fan relay. The low speed GM would splice to BR/GE (brown/yellow) wire going to TS on the Porsche fan relay. Is this correct?

Yes, the GM PCM sends a ground signal to activate the fans. I wouldn't recommend using any of the Porsche original system, its pretty simple to wire it like gm did, easier on the electrical components, and less likely to catch your car on fire. I have the diagram on my laptop if you need it.

Mark

Thanks, I have the 3 relay diagrams. I know so little about this it makes me easily influenced and I change my mind daily. The two wire hookup is going to be easier, the three relay system is how the ECM was designed to work.

here's what I ended up doing. I had to remove the windshield washer reservoir to get some extra space to mount the relays and my alarm siren. It was cracked somewhere and leaked anyway. I ran all the wiring down a channel where the hood sits. I used a 10ga wire to the battery with a 40amp fuse. I already had the 30/40 relays and harnesses so I used them. Will see how long they last. I'll eventually replace them with some 40/50's or higher.

Admin wrote:Are you using the factory fans?

If so, why are you going through all the trouble of rewiring them. All you have to do is hook up two simple wires from the PCM to the factory 2 speed relay and your done. NO wire size to worry about , NO wiring diagram to worry about , NO finding fuses and hiding everything to look right.

Are you just grabbing the two wires under the fuse/relay panel?

Yes, from what I can tell from the electrical schematics. Basically, you are replacing the switch that is in the Porsche radiator with the GM ECM. I like this idea, cut and splice two wires and simplify the fans and A/C system control all at once.

I took the high and low speed Porsche relay wires from the thermofan switch at the radiator. The thermofan switch won't be used so I cut the connector off and pulled the wires back through the harness covering on that side, routed them over to the passenger side and soldered them to the respective GM high/low speed fan relay wires.

That's the way to do it!

Arthropraxis wrote:I took the high and low speed Porsche relay wires from the thermofan switch at the radiator. The thermofan switch won't be used so I cut the connector off and pulled the wires back through the harness covering on that side, routed them over to the passenger side and soldered them to the respective GM high/low speed fan relay wires.

Any updates on this idea? Has anyone had ANY problems with there fans being wired like this? How many trouble free miles have you put on your "new Porsche"?